How to Convert EV Into F-Stop

LV, or Light Value, measures the brightness of the subject you are photographing. To expose an image correctly, you need to convert LV to EV, or Exposure Value, which is the measure of the light to which your film or digital sensor is exposed when you press the shutter release. EV is a combination of film speed, lens aperture measured in f-stops and shutter speed. LV and EV are normally determined with spotmeters to set exposures for traditional film cameras, especially medium and large formats.

Instructions

LV, EV and Camera Settings

1

Measure light value with a spotmeter. LV ranges from L-15, when the only light source is starlight, to L18, noon sun on open snow. LV7 is typical indoor light, or outdoors 10 minutes before sunrise or 10 minutes after sunset. Sunset scenes are LV 9-10. LV13 is bright shade or light overcast day. Gray cards in full sunlight are LV 15-16.

2

Convert LV to EV. Most classic spotmeters have built-in converters that you can use to translate LV to EV. Many conversion tables are available online. A simple way to convert LV to EV yourself is to remember that" EV = LV at ISO 100," and that LV and EV both have one f-stop increments. With 50 ISO film, expose LV 14 at EV 13. For ISO 400, expose an LV 12 subject at EV 14.

3

Convert EV to actual exposure settings. The EV scale starts at EV 0, or f/1.0 at one second. If you are shooting 100 ISO film in typical afternoon sunlight with the subject sidelit, then: LV 14 = EV 14 = f/8 at 1/125 second.

4

Use the "sunny 16" rule if you do not have a light meter and need to estimate approximate exposure value. "Sunny 16" is the rule that in bright sunlight you expose at f/16 at the reciprocal of the film speed. For ISO 100 film, that would mean f/16 at 1/125. Use an EV table to calculate f-stops off "sunny 16" for given lighting situations.